Manufacture of sheet-iron



E (No'ModeL) I. E. CRAIG.

MANUFACTURE OF SHEET IRON.

N0. 321,693. Patented July '7, 1885.

N fizz/en? I Jaw NirEn STATES PATENT @rricn,

ISAAC n. CRAIG, or CAMDEN, OHIO.

MANUFACTURE OF SHEET-IRON.

fiPECIFICATION forming part of-Letters Patent No. 821,693, dated July 7,1885.

Application filed July 10, 1884.

To all whom 25 may concern:

Be it known that I, ISAAC E. CRAIG, a citi zen of the United States,residing at Camden, in the county of Preble and State of Ohio,haveinvented a certain new and useful Improvement in the Manufacture ofSheet-Iron,whereby I am enabled to manufacture a superior quality ofpolished sheet-iron to that heretofore made.

I do hereby declare the following to be a full, clear, and exactdescription of the invention, which will enable others skilled in theart to which it appertains to make and use the same.

As uniformly practiced polished sheet-iron is manufactured from sheetsor slabs having at some stage near which the process or operation ofpolishing is begun little or no oxide on their surfaces, and when oxideof any considerable thickness has formed, as is usually the case in theearlier steps of heating and rolling, they are cleansed of their oxideeither by dissolving away the oxide in baths of suitable acids or byrestoring the oxide to metallic condition by heating for a considerabletime in packs with layers of charcoal between them.

This invention is useful where either method of cleaning is resorted to,or where the sheets without being cleaned have but a thin coating ofoxide.

I have discovered that when oxide of lead or a salt of lead or oxide oftin or a salt of tin is applied in small quantities to the surface ofsheet or slab iron and exposed to a red heat, if graphite be alsopresent in contact with the oxide or salt or in contact with themetallic lead or tin resulting from the decomposition of the oxide orsalt, that the lead or tin in the state of metal unites by chemicalaction or. mechanical mixture with the graphite, and forms on thesurface of the sheets or slabs a coating which possesses some of theproperties of both the metals and the graphite, but, unlike graphite, isfusible, and will not rub off, and, unlike the metal, has some capacityfor a durable luster, and that in the subsequent working of the sheetsat a heat while being polished the metals and graphite become mingledand incorporated with the new oxide on the surface of the sheetsin such(No model.)

a way as to give to the surface a close texture, ability to resistcorrosion, and a handsome appearance. The presence of this mixture onthe surface of the sheets prevents the development in finishing of redor brown spots or patches, which are a source of much loss in themanufacture of polished sheets.

It is already known that an improvementis made in the quality of thesurface of polished sheet-iron by applying, during its manufacture, tothe sheets or slabs a small quantity of oxide of lead or oxide of tin,so that on being reduced their metals may unite with the surface andproduce, as they are found to do, a desirable tenacity and flexibilityof oxide on the finished sheets. It is also known that an improvementresults from the presence on the sheets during the latter steps of theirmanufacture of a small quantity of graphite, and that graphite so usedgives adaptability to polish, uniformity of color, and chemicalinertness to the surfaces so produced. But the qualities resulting fromthese two methods of treatment have not heretofore been obtained on thesame sheets; and I find in practice that where lead or lead and tin arerevived on the sheets from the oxide or salts, in the after working ofthe sheets without the presence of graphite a part of the lead on amajority of the sheets reoxidizes and fuses into the wellknown red,glassy, and brittle form of fused litharge, and of the remainder of thesoft metals not so reoxidized a part is gathered into grains or speckson the surfaces in finishing. I also find that where graphite is used,although favoring in the highest degree the acquisition of luster,without the presence of lead or tin, the surface produced lacksflexibility and attachment to the body of the iron on being bent. And Ifurther find that graphite, unlike other forms of carbon, does not actas a reagent to reduce the metallic oxides, as its lowest temperature ofcombustion is much above the highest heat used in making sheetiron, butthat it remains, forming chemical union or mechanical mixture with therevived metals and the surface of the iron, and that the oxides arereduced by the hydrogen occluded within the iron, or. by thehydrocarbons in the heated atmosphere of the furnace; and that thisreduction is accomplished as well when the coating of oxides andgraphite is a mixture of these solids with water as when oil or othercarbonaceous matter is used. I also find that the several defects asabove de scribed attending the separate use of the materials nameddisappear when the materials named are jointly used.

The object of this invention is to produce all these beneficial effectson the same sheets by the application of the materials above named; andto this end my invention consists in the following treatment of thesheets or sheetslabs which have but a thin coating of oxide or have beencleansed of their coating by any of the means known to the art.

In the annexed sheet of drawings, Figures 1 and 2 show the method ofapplying the mixture.

I prepare a mixture of oxide of lead or salts of lead and graphite orthe oxide or salt of tin and graphite, or of all three, using bypreference, and as I think best for use on slabs, four pounds of oxideof lead, litharge rather than red lead, one-quarter pound of oxide oftin, known as putty powder or polishing-powder, and onepound ofgraphite,ground together inone gallon of any suitable fluid, by preferencelinseed-oil, and apply this by a wide brush or other convenient means tothe surfaces of each sheet or slab to be operated on. In those caseswhere in the process of manufacture the iron is cleaned in sheet-slabsand the oxide is removed by acids they should have this paint applied tothem in the manner shown at A in Fig. 1 of accompanying drawings beforebeing again heated; so,also, where the oxide is thin and not removed thepaint should be applied to the iron when in the slab,and if deoxidizedbyheating the slabs with interlayers of charcoal or other deoxidizingagent the paint should be applied when they are being piled up in theform shown at B for this operation,andbefore the application of thecharcoal powder, and is not in danger of being removed when the charcoalis afterward swept away, as it is then firmly attached to the surface.These slabs should not be more than about three times as thick as thesheets are intended to be when finished. The slabs may then be workeddown to sheets in the ordinary manner of rolling at moderate redheat,will roll without sticking one to another, and will acquire someluster in being so reduced. They should then be heated and polished inpacks in the usual manner under steam-hammers. When the sheets arecleaned at about the gage at which they are to be finished, the mixtureof graphite,oxide,and oil should be made with but one-third so muchoxides and graphite to a given quantity of oil as that stated as thecorrect proportions for use on slabs and applied in the manner shown atA in Fig. 2 before being piled up as shown at B. They should, ifcleansed with acids, or if desired to treat at this stage withoutcleansing from a thin oxide, be heated to high redness with the paint onin the annealing or other convenient furnace in packages, and whenwithdrawn opened so as to expose each sheet to the air while red hot tocolor and reoxidize the iron; and if at this thickness they aredeoxidized with charcoal and heat the paint should be first applied,and,when deoxidized,should be swept of their charcoal while still redhot, so as to give access of air on their surfaces while at a hightemperature. In either case, after having been painted, heated, andrcoxidized as described, they are ready to be reheated and polished inpacks under the harm mer in the usual manner. In each of theseoperations I find it most economical and desirable to apply the oxidesand the graphite at one and the same time and already mixed together;but I do not confine myself to that method alone, as I find that theymay be applied separately, and even with one or more heats of the ironintervening,if there is a heat and application of mechanical force inrolling or hammering after the last is applied, and their intermixtureand union with the surface in a great degree still take place. Iron somade combines the excellent qualities already described.

Having fully described my invention,what I claim, and desire to secureby Letters Patent, 1s

An improvement in the manufacture of sheetiron, consisting in coatingthe surface during the process of manufacture with acomposition ofmatter before the final heat and working, consisting of graphite and theoxide or a salt of either or both tin and lead.

ISAAC E. CRAIG.

\Vitn esscs:

O. P. BRowN, C. E. GUILD.

